Titanium-base alloys



2,829,974 TITANIUM-BASE ALLOYS Walter L. Finlay and Howard T. Clark, Ira, Beaver, Pa., andJohn A. Snyder, Wilmington, Del assignors to Rem-Cru Titanium, Ina, Midland, Pa., a corporation of Pennsylvania No Drawing. Application October 8, 1952 Serial No. 313,794

5 Claims. (Cl. 75-41755) This invention pertains to titanium-base alloys and more specifically to ternary and quaternary alloys of titanium with two or more of the elements chromium, molybdenum and manganese.

Thisapplication is a continuation-in-part of our copending applications Serial No. 134,774, filed December 23, 1949, now abandoned, and Serial No. 268,934, filed January 29, 1952, now Patent 2,787,541.

The low temperature or alpha phase of substantially pure titanium, which is of close-packed hexagonal structure, transforms at a temperature of about 885 C., to the hightemperature or beta phase, which is of body-centered cubic structure. The presence of such contaminants or alloying agents as carbon, oxygen and nitrogen, in the proportions in which they are commonly found in commercial titanium, tends to raise the beta transformation temperature, and establishes a relatively narrow zone or fieldof mixed alpha-beta structure. The presence ofcertain alloying metals, prominent among which are chromium, manganese and molybdenum, has a quite diiferent effect upon'transformation. Increasing amounts of these alloying materials tend to stabilize the beta phase at progressively lower temperatures and establish a mixed alphabeta field of substantial scope.

It has been found. that the alloying with titanium of about 12 atomic percent of two or more of the metals manganese, molybdenum and chromium, can be processed to substantially stabilize the titanium in the beta phase at room temperature. The present invention contemplates a group of alloys in which the beta phase has been thus stabilized. Lesseradditions of the elements aforesaid result in alloys of excellent properties having a mixed alpha-beta microstructure, and these are likewise contemplated by the present invention.

While atomic percent has been referred to in the preceding paragraph, the proportions appearing elsewhere in this specification and in the claims are weight percent.

The ternary Ti-Mn-Mo alloys of the invention are typified as to strength and ductility by the test results for various analyses given in Table I below:

TABLE I The physical properties of ternary Ti-Mn-Mo alloys after a 1-hour vacuum anneal at 700 C.

Composition,

percent Tensile properties, (balance p. s. 1. Percent titanium) Ti base 1 elong.

1 OP refers to titanium of commercial purity obtained by magnesium reduction of titanium tetrachloride according to Kroll U. S. P. 2,205,854, while iodide" refers to high purity titanium obtained by the iodide process of Van Arkel U. S. P. 1,671,213.

2,829,974 Patented Apr. 8, 1958 It will be seen from the foregoing results that the Ti-Mn-Mo ternaries within the range of about 1 to 15% manganese and 1 to 25% molybdenum have good strength combined with adequate ductility. These alloys have in general at room temperature a mixed alpha-beta microstructure, conducive to relative ease of fabrication, forging, rolling, etc., as compared to the all-alpha or allbeta alloys, while maintaining comparable strengths at room temperature.

Considering now the ternary Ti-Mn-Cr alloys of the invention, Table II below gives test data corresponding-to Table I for typical analyses:

TABLE II The physical properties of ternary Ti-Mn-Cr alloys after a 1-hour vacuum anneal at 700 C.

Composition,

percent Tensile properties, (balance p. s. 1. Percent titanium) Ti base clong.

Mn Or Yield Tensile For the alloys of this group having good strength combined with suificient ductility for fabrication purposes, the useful range'is about 2 to 12% chromium with about 2 to 15% manganese.

It will be seen by comparison of Tables I and II that the Ti-Mn-Cr ternaries have considerably higher strength than the Ti-Mn-Mo ternaries, and the same is true with respect to the T'-Cr-Mo ternaries described below. The Ti-Mn-Cr alloys in general have a mixed alpha-beta microstructureat normal or atmospheric temperatures.

Table'III below gives strength and ductility data on typical Ti-Cr-Mo ternary alloys according to the invention:

The alloys having a combined content of about 3.0 to 12% of Cr and Mo have a mixed alpha-beta microstructure, while those above 12% combined Cr and Mo have in general a stable beta structure at normal temperatures.

Table IV below gives the physical properties of typical quaternary Ti-Mn-Cr-Mo alloys according to the invention:

"TABLE IV The physical properties of quaternary Ti-Mn-Cr-Mo alloys after a I-hour vacuum anneal at C. W

Composition, percent Tensile properties,

(balance titanium) p. s. 1.. Percent Tl base elong.

Mn Cr Mo Yield Tensile It will be seen that these alloys possess in general high Strength combined with high ductility. That these alloys possess in general a stable beta microstructure, is shown by the bend test data of the following Table V, which gives bend test values of typical analyses as annealed and after subsequent aging for 16 hours at 400 C. and after 68 hours at 300 C.:

TABLE V Bend ductility T of samples after 1 hr. 700 C. vacuum anneal followed by heat treatment shown It will be observed that these analyses undergo no substantial change in bend ductilities as a result of these aging treatments, which indicates that there has been no rejection of a second phase.

The useful range for the ductile quaternary alloys of Tables IV and V is about 1.0 to 25% molybdenum with about 1 to 15% manganese and about 1 to 12% chromium. A preferred range for assuring optimum beta stability is about 4 to 11% manganese without 2 to each of chromium and molybdenum and an aggregate content of these elements of about 17 to 23%. A particularly good alloy is one containing about 10% manganese and 5% each of chromium and molybdenum.

The alloys of the invention are preferably made by melt casting, and may optionally contain up to about 0.3% carbon, and up to 0.2% each of oxygen and nitrogen.

Depending upon the particular sample tested, unalloyed iodide titanium has approximately a yield strength of 27,000 p. s. i., a tensile strength of 43,000 p. s. i., an elongation of 40% and a bend ductility of 0.

Again, depending upon the sample tested, the corresponding values for unalloyed titanium of commercial purity are approximately: yield strength 51,000 p. s. i., tensile strength 76,000 p. s. i., elongation 21%, bend ductility 5 0.8.

It will be seen by comparison of the above values for unalloyed titanium with those of Tables I-V, inc., herein, that the tensile properties of the alloys of this invention are tremendously enhanced as compared to the unalloyed titanium, while maintaining adequate ductility for purposes of fabrication. As shown by the test data of these tables, the tensile strength of the alloys hereof ranges from a minimum of about 110,000-115,000 p. s. i. to as high as about 190,000 p. s. i. Expressed in percentages, the increase in tensile strength of the alloys herein as compared to unalloyed titanium of commercial purity, ranges from about 50% to 250%.

What is claimed is:

l. A stable and ductile alloy containing at least two elements selected from the group consisting of about 1 to manganese, about 3 to 12% chromium, and about 1 to molybdenum, said alloy also containing up to 0.3% carbon and up to 0.2% each of oxygen and nitrogen, balance titanium.

2. A thermally stable and ductile titanium base alloy containing about 4 to 11% manganese, about 2 to 10% each of chromium and molybdenum, up to about 0.3% carbon, up to about 0.2% each of oxygen and nitrogen, said alloy being characterized in having an ultimate strength in excess of the unalloyed titanium base metal,

and in undergoing no appreciable loss of ductility o aging at temperatures up to about 400 C.

3. A stable and ductile alloy containing about 4 to 11%- manganese, about 2 to 10% each of chromium and 0.2% each of oxygen and nitrogen, and the balance titanium. v 4. A thermally stable titanium base and ductile alloy each of chromium and molybdenum, the total content of these elements being about 17 to 23%, up to about 0.3%- carbon, up to about 0.2% each of oxygen and nitrogen,

said alloy being characterized in having an ultimate References Cited in the file of this patent UNITED STATES PATENTS 2,588,007 Iatfee Mar. 4, 1952 2,596,485 Iattee et al. May 13, 1952 FOREIGN PATENTS 718,822 Germany Mar. 24, 1942 OTHER REFERENCES Titanium, Report of Symposium December 16, 1948, sponsored by O. No. R., Dept. of the Navy, page 140.

Product Engineering, November 1949, pages 149 and 150.

molybdenum, up to about 0.3% carbon, up to about containing about 4 to 11% manganese, about 2 to 10%- strength in excess of the unalloyed titanium base metal, and in undergoing no appreciable loss of ductility 'on' UNITED STATES PATENT OFFICE CERTIFICATE OF CDRTIECTION Patent No. 2,829,974

April 8, 1958 Walter L. Finlay et al.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 55, for 'without 2 to 10%" read 5- with about 2 to 10% Signed and sealed this 27th day of May 1958,

(SEAL) Attest:

KARL H. AEINE ROBERT C. WATSON Attesting Officer Conmissioner of Patents 

1. A STABLE AND DUCTILE ALLOY CONTAINING AT LEAST TWO ELEMENTS SELECTED FROM THE GROUP CONSISTING OF ABOUT 1 TO 15% MANGANESE, ABOUT 3 TO 12% CHROMIUM, AND ABOUT 1 TO 25% MOLYBDENUM, SAID ALLOY ALSO CONTAINING UP TO 0.3% CARBON AND UP TO 0.2% EACH OF OXYGEN AND NITROGEN, BALANCE TITANIUM. 